RE: Extract variable string from a based DS using a pointer

["Bob Cozzi" <cozzi@xxxxxxxxx>]

You've got it right.
-Bob

-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx [mailto:rpg400-l-bounces@xxxxxxxxxxxx]
On Behalf Of Dave Murvin
Sent: Thursday, December 16, 2004 6:29 PM
To: RPG programming on the AS400 / iSeries
Subject: RE: Extract variable string from a based DS using a pointer

Thanks Bob,

This data structure is one of many that can be filled in by an API.  I 
guess I didn't previously understand about no storage being allocated when 
using BASED.

Let me rephrase your answer.

If I declare TextData as a 32K variable then assign a value to the textPtr, 
as long as I don't excede the textLen (as returned by the API) when I 
reference TextData, I should be okay. Any TextData characters beyond the 
TextLen specified can be anything in that happens to be in that area of 
memory, but I do not have a full 32K field allocated.  Do I have this right?

I thought about a VARYING field, but since this is a structure returned by 
an API, I didn't think the variable field would be populated correctly by 
the API (it would return data in the two length bytes).

At 03:40 PM 12/16/2004, you wrote:
>Are you trying to simulate a VARYING field? Looks like it to me.
>
>D TextDS    DS                       BASED(textPtr)
>D  TextLen                     5I 0
>D  TextData                32766A
>
>
>If you use BASED, no storage is allocated for TEXTDS, so it does not matter
>if you declare TEXTDATA as a 32K variable. That way SUBST and other
>operation will work the way you want.
>
>If you want to NOT use this suggestion, and you simply want to copy from
>that memory location, use this:
>
>   Eval     memcpy(%addr(target) : textPtr + 2: some-length-here )
>
>
>
>But why not just use a VARYING field?

Dave Murvin
DRM Enterprises, Inc.


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